We shall continue our studies on silicate transport and its mechanism in the diatom Nitzschia alba. Comparative studies will be conducted on intact cells, protoplasts, and isolated cytoplasmic membrane vesicles. We shall attempt to answer the following questions: 1. Is the energy for silicate transport provided by oxidation, by the membrane-bound (Na ion-K ion)-ATPase, or by both? 2. Is silicate transport electrophoretic or neutral? 3. Does silicate enter by uniport, by symport with cations or by antiport with anions? We shall also continue our studies on the role of silicon in the synthesis of DNA and DNA polymerases. We shall study the effect of silicon on the regulation of mRNA and protein synthesis in the diatom Cylindrotheca fusiformis.